github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-09-22 12:44:03 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

mm/slab: use call_rcu() in unknown context if irqs are enabled

Browse Source 
call_rcu() disables IRQs with local_irq_save() to protect its per-cpu
data structures. Therefore, if IRQs are not disabled, they cannot be
corrupted by reentrance into call_rcu(). So fall back to the deferred
path only when !allow_spin && irqs_disabled().

The RCU subsystem does not guarantee this contractually, and this
optimization relies on RCU's implementation details. Ideally, it should
be removed once call_rcu_nolock() is supported by the RCU subsystem.

Link: https://lore.kernel.org/linux-mm/CAADnVQKRVD5ZSnEKbZZU7w86gHbGHUug2pvzpgZTngNS+fg4rw@mail.gmail.com
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Harry Yoo (Oracle) <harry@kernel.org>
Link: https://patch.msgid.link/20260729-kfree_rcu_nolock-v5-3-a28cdcda9673@kernel.org
Reviewed-by: Shengming Hu <hu.shengming@zte.com.cn>
Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
This commit is contained in:
Harry Yoo (Oracle) 2026-07-29 17:20:11 +09:00 committed by Vlastimil Babka (SUSE)
parent f3521fbec2
commit f8e0c30599
1 changed files with 6 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
mm/slub.c
View File

@ -6132,8 +6132,12 @@ bool __kfree_rcu_sheaf(struct kmem_cache *s, void *obj, unsigned int free_flags)
if (likely(rcu_sheaf->size < s->sheaf_capacity)) {
rcu_sheaf = NULL;
} else {
if (unlikely(!allow_spin)) {
/* call_rcu() cannot be called in an unknown context */
/*
* With !allow_spin, we might have interrupted call_rcu()'s
* IRQ-disabled critical section. If IRQs are not disabled,
* we know that's not the case.
*/
if (unlikely(!allow_spin && irqs_disabled())) {
rcu_sheaf->size--;
local_unlock(&s->cpu_sheaves->lock);
goto fail;